Except for numbers, don't believe there's much difference between the carbs. I would still go the Promax route. You can a least reset and adjust idle mixture. All 3 carbs contribute when idling, not just the center carb. You can not adjust the rear carb with the stock baseplate. When they are right, they hit like a freight train. I have tried 440 carbs on my 418, they aren't much different.